\documentclass{standalone}
\usepackage{tikz}
\usepackage{circuitikz}
\begin{document}
\usetikzlibrary{positioning,shapes,arrows,snakes}
\definecolor{yellowish}{HTML}{FFE699}
\definecolor{grayish}{HTML}{D9D9D9} 
\tikzset{
   rect/.style={
      align=center,
      text=black,    
      minimum width=2.5cm,
      minimum height=2cm}
}
\tikzset{
   done/.style={rect, fill=grayish }
}
\tikzset{
   todo/.style={rect, fill=yellowish}
}
\tikzset{
   arrow/.style={line width=1mm}
}
\tikzset{block/.style = {draw, fill=white, rectangle,
                     minimum height=3em, minimum width=2cm},
           input/.style = {coordinate},
           output/.style = {coordinate},
           pinstyle/.style = {pin edge={to-,t,black}}
       }
\centering

\begin{tikzpicture}[auto, node distance=2cm,>=latex',font=\sffamily\small]
   \node[block](tx)                            {zender};
   \node[block,right = 6cm of tx](rx)          {ontvanger};
   \node[antenna](txant) at (tx.north) {};
   \node[antenna,xscale=-1](rxant) at (rx.north) {};
   \draw[snake=expanding waves] 
     (txant.east) -- ++(1,0) coordinate(begin);
   \draw[ultra thick,gray] 
     (begin) -- ++(2,0) coordinate(midden);
   \draw[->,ultra thick, gray] 
     (midden) -- ++(2,0) node[right,align=center]  {Ontvangen\\vermogen \textbf{Pr}};
   \draw (midden) node[align=center, below]        {transmissieverlies\\\textbf{Lp}};
   \node[above=1cm of txant.north,align=center]    {Antenneversterking\\zender \textbf{Gt}};
   \node[above=1cm of rxant.north,align=center]    {Antenneversterking\\ontvanger \textbf{Gr}};
   \node[above right = 1 cm of txant.east,align=center]     {Zendvermogen\\\textbf{Gt}};
\end{tikzpicture}
\end{document}